Bug 1467658 - Upgrade the default clang toolchain to clang 6. r=chmanchester

The linux64-clang toolchain alias is currently clang 5. Switch it to
clang 6, but keep the spidermonkey tsan builds on clang 5 because of
bug 1467673.

The LLVM headers that come with clang 6 contain a DEBUG define that
conflicts with our DEBUG define and breaks the clang-plugin build,
so force unset ours.

--HG--
extra : rebase_source : aae88f1166108f003b06c022f14d5f4c61fc1ed9

build/clang-plugin/moz.build

@@ -98,3 +98,7 @@ for var in ('LINKER', 'OPTIMIZE'):
 if CONFIG['HOST_OS_ARCH'] == 'Linux' and CONFIG['OS_ARCH'] == 'Darwin':
     # Don't pass OSX linker arguments.
     LINK_FLAGS['FIX_LINK_PATHS'] = []
+
+# Avoid -DDEBUG=1 on the command line, which conflicts with a #define
+# DEBUG(...) in llvm headers.
+DEFINES['DEBUG'] = False

taskcluster/ci/spidermonkey/linux.yml

@@ -138,6 +138,8 @@ sm-tsan-linux64/opt:
         platform: linux64/opt
     run:
         spidermonkey-variant: tsan
+    toolchains:
+        - linux64-clang-5
 
 sm-rootanalysis-linux64/debug:
     description: "Spidermonkey Root Analysis"

taskcluster/ci/toolchain/linux.yml

@@ -65,7 +65,6 @@ linux64-clang-5:
             - 'build/build-clang/build-clang.py'
             - 'build/build-clang/clang-5-linux64.json'
             - 'taskcluster/scripts/misc/tooltool-download.sh'
-        toolchain-alias: linux64-clang
         toolchain-artifact: public/build/clang.tar.xz
     toolchains:
         - linux64-gcc-4.9
@@ -87,6 +86,7 @@ linux64-clang-6:
             - 'build/build-clang/build-clang.py'
             - 'build/build-clang/clang-6-linux64.json'
             - 'taskcluster/scripts/misc/tooltool-download.sh'
+        toolchain-alias: linux64-clang
         toolchain-artifact: public/build/clang.tar.xz
     toolchains:
         - linux64-gcc-4.9